Consumer Surplus:

In economics, the consumer surplus is a measure of the consumer welfare gained from the consumption of goods. The consumer surplus from a unit of a consumption good is the difference between the marginal willingness to pay for the good and the actual price paid.

Answer and Explanation:

A. The quantity sold is 100.

The consumer will buy until the marginal willingness to pay is the same as the market price.

For example,

{eq}p(x) = 100 - x + 0.001x^2 = 10 {/eq},

which yields

{eq}x = 100{/eq}.

B. The consumer surplus is the sum of the consumer surplus generated from each unit sold.